"IL-36" redirects here. For the road formerly known as Illinois Route 36, see Illinois Route 94.
Interleukin 36, or IL-36, is a group of cytokines in the IL-1 family with pro-inflammatory effects. The role of IL-36 in inflammatory diseases is under investigation.[1]
There are four members of the IL-36 family which bind to the IL-36 receptor (IL1RL2/IL-1Rrp2/IL-36 receptor dimer) with varying affinities.[2]IL36A, IL36B, and IL36G are IL-36 receptor agonists. IL36RA is an IL-36 receptor antagonist, inhibiting IL-36R signaling. The agonists are known to activate NF-κB, mitogen-activated protein kinases, Erk1/2 and JNK through IL-36R/IL-1RAcP, which targets the IL-8 promotor and results in IL-6 secretion and induces various proinflammatory mediators.[3][4] Binding of the IL-36R agonists to IL-1Rrp2 recruits IL-1RAcP, activating the signaling pathway. IL-36Ra binds to IL-36R, preventing the recruitment of IL-1RAcP.[1]
Function
IL-36 has been found to activate T cell proliferation and release of IL-2.[5] Before the functions of the IL-36 cytokines were determined, they were named as derivatives of IL-1F; they were renamed to their current designations in 2010.[6]
The genes encoding for the IL-36 cytokines are found on chromosome 2q14.1.[8][9][10] All three are located in a cluster with other members of IL-1 family and the gene order from centromere to telomere is IL-1A-IL-1B-IL-37-IL-36G-IL-36A-IL-36B-IL-36RN-IL1F10-IL-1RN, and only IL-1A, IL-1B and IL-36B.[11] All of them probably arose from a common ancestral gene, which is most likely a primordial IL-1 receptor antagonist gene.[12]
All three genes are mainly expressed in keratinocytes, bronchial epithelium, brain tissue, and monocytes/macrophages.[6] In the epidermis IL-36 cytokine expression is limited to granular layer keratinocytes with little to no expression in basal layer keratinocytes.[13]
IL-36Ra is constitutively expressed in keratinocytes, whereas IL-36γ expression in keratinocytes is rapidly induced after stimulation with TNF or PMA (Phorbol 12-myristate 13-acetate).[14]
Clinical significance
IL-36-alpha functions primarily in skin and demonstrates increased expression in psoriasis. In addition, decreased expression of this gene has been linked to a poor prognosis in both hepatocellular carcinoma and colorectal cancer patients.[6]
Studies revealed that T cells were sufficient to cause skin inflammation after Staphylococcus aureus exposure on mice, mediating the skin inflammation via IL-36-controlled, IL-17-dependent T cell responses.[16]
IL-36 is significantly involved in the pathogenesis of psoriasis leading to it being targeted therapeutically. Human psoriatic skin plaques displayed elevated IL-36beta. In addition, It was found that serum IL-36 levels are higher in patients with psoriasis vulgaris and its levels positively correlate with disease activity, suggesting that serum IL-36 levels might serve as useful biomarkers in patients with psoriasis.[17]
^ abcdeGresnigt MS, van de Veerdonk FL (December 2013). "Biology of IL-36 cytokines and their role in disease". Seminars in Immunology. 25 (6): 458–65. doi:10.1016/j.smim.2013.11.003. PMID24355486.